On September 22nd the design for an observation tower for the nature reserve 'De Onlanden', situated to the southwest of Groningen, was presented to Natuurmonumenten (the Dutch Society for the Preservation of Natural Heritage) during the mini-symposium 'Experience Nature with innovative concrete' in Peize.
The observation tower is the result of a study into the optimal application of Ultra High Performance Concrete by a case study team comprising of UNStudio, ABT, BAM Utiliteitsbouw en Haitsma Beton. Natuurmonumenten received the design as a gift from the case study team.
Case Study Observation Tower Ultra High performance Concrete
The design for the observation tower is the result of a case study which aimed to apply the characteristics of Ultra High Performance Concrete in a functional, operative design. The case study team consisted of designers, engineers and builders who together sought a solution through which architecture and construction could reinforce one another. According to Ben van Berkel, "The observation tower afforded our Inventive Materials Research Platform the opportunity to investigate the properties of Ultra High Performance Concrete and to truly test out the full potential of this new material in a real structure." Ultra High performance Concrete differs from normal concrete as it has a very high density, contains steel fibres and has an extremely fine grain structure. These properties facilitate the application of large compressive stresses in structures of narrow dimensions. UNStudio's Inventive Materials Platform is one of four in-house research platforms and aims to investigate custom-made material applications and to facilitate inspired and imaginative collaborations with other experts and with manufacturers in the construction industry.
The 25 metre high observation tower will be realised on the forested boundary of 'De Onlanden' nature reserve on the outskirts of Groningen. Once built, the tower will extend 5 metres above the trees and will offer views over the 3,000 hectares of natural landscape which form the largest water storage area in the Netherlands.
The design for the observation tower guides visitors in a fluid ascent up the 134 steps to the highest viewing point. Visitors are lead via the first set of steps to the lower viewing platform which stands at a height of 10 metres. Following this, the second set of steps provides a turn in direction, allowing for an alternative view of the surrounding forested pastures. These steps lead visitors through the tree tops to the second viewing platform which stands at a height of 20 metres and offers views over the nature reserve around the city of Groningen. The highest viewing platform, at a height of 24 metres, is reached via the final set of steps and offers visitors a wide open vista of 'De Onlanden' nature reserve.
By means of changes in direction in the structure of the observation tower, visitors can experience views of the surrounding natural landscape from different perspectives, whereby the height of each viewing platform offers a different experience of the vistas over the surrounding landscape. From the highest viewing platform views are afforded of the Groningen skyline, which includes the Education Executive Agency & Tax office building which was also designed by UNStudio.
The fine lines and the form of the tower bring to mind the silhouette of a deer.
The observation Tower is a hybrid construction, consisting of a combination of steel and Ultra High Performance Concrete. Steel is employed where the tensile stresses are foremost, whereas Ultra High Performance Concrete manifests excellent performance properties where the compressive stresses are highest. The parapet around the stairs and platforms is constructed from stainless steel mesh, enabling the combination of both maximum transparency and necessary safety levels. Ben van Berkel: "The strength of Ultra High Performance Concrete is conceptually expressed in the cantilever of the structure, which combines UHPC with steel to enable a substantial protraction in the form of the viewing tower."
